There is a reason why certs have expiration dates. It's to control the damage after the site owner or someone else in the cert chain messes up. That doesn't mean expired certs are inherently not secure, only that you should still care about it and do your best to avoid using expired certs.

No, but it reflects poorly on the maintainer. Plus, any browser complaint contributes to error fatigue. Users shouldn't just ignore these, and we shouldn't encourage them to ignore them just because we fail at securing our websites.

Back when I was using it, mathematica was unmatched in its ability to find integrals. Has python caught up there?